Mobile devices (e.g. mobile telephones) typically operate using multiple frequency sources. The first frequency source is a high-frequency crystal clock (e.g., having a reference frequency of 26 MHz) used in active modes, such as when communicating with the cellular base-station or performing high frequency processing. The second frequency source is a low-frequency clock (e.g., having a reference frequency of 32 kHz) that is used for maintaining a time base during idle states. The second, low-frequency clock avoids current consumed in generating and distributing the high frequency clock source, as well as current consumed in devices connected to the high frequency clock that do not implement adequate clock gating.
According to conventional designs, separate circuits having different components are required to utilize the high frequency and low frequency sources.